1. Field of the Invention
The present invention relates to an apparatus for dispensing a predetermined amount of cells contained in a hydrophilic suspension, and more particularly, to an apparatus for dispensing a predetermined amount of cells by analyzing the number of cells contained in the liquid droplet while manipulating a liquid droplet of a hydrophilic suspension using an electrowetting-based liquid droplet manipulation unit. The present invention may be used for dispensing a predetermined amount of cells required for manufacturing of a cell chip, or dispensing a predetermined amount of minute particles dispersed in a hydrophilic liquid.
2. Description of the Related Art
Generally, a cell chip means a microchip used for fixing cells such as bacteria, animal cells on a surface of a solid substrate made of silicon, surface-modified glass, polypropylene, or activated polyacrylamide, and analyzing various reaction patterns such as gene expression patterns, genetic defects, and protein generation. Since a complicated physiological signal from a cell that has not been measured by a conventional method can be detected through real-time reaction of a living cell, microchip is very useful.
To manufacture a cell chip, dispensing a predetermined amount of cells is required. To manufacture a cell chip of high integration, a very small amount of a suspension droplet is dispensed onto a narrow region on a substrate because uniformity in the number of cells contained in this minute liquid droplet is required. A variety of methods and apparatuses have been proposed to dispense, in a minute liquid droplet, suspension of a bio material such as deoxyribo nucleic acid (DNA), protein, and animal cells. However, a constant volume of a minute liquid droplet does not necessarily mean that bio materials contained in the minute liquid droplet is dispensed by a constant amount.
Particularly, when cell suspension is dispensed, a particle (cell) size is large and so it is difficult to uniformly disperse cells inside the suspension. Accordingly, the number of the cells contained in a liquid droplet cannot be controlled. Also, as time elapses, the cells contained in the suspension easily cohere and viscosity of the suspension changes, which makes it more difficult to dispense a liquid droplet by a constant volume, and a deviation in the number of cells contained in each liquid droplet increases. To uniformly disperse the cells inside the suspension, a method of reducing the number of cells per unit volume, i.e., density of cell suspension may be considered. However, when density is reduced to about 105 cells/ml (=10−4 cell/pl), 10,000 times of dispensing should be performed in order to dispense by 1 pl and obtain a liquid droplet containing one cell. Accordingly, efficiency remarkably decreases when a cell chip is manufactured.
Therefore, an apparatus capable of dividing cell suspension into minute liquid droplets, and simultaneously, quantitatively dispensing the liquid droplets such that a desired number of cells are contained in each liquid droplet, is highly required.